A single-blind field intervention study of whether increased bedroom ventilation improves sleep quality.

A four-week-long field intervention experiment was conducted in twenty-nine bedrooms with extract ventilation systems and air inlet vents. During the first week no interventions took place. In the three weeks that followed, each participant slept for one week under a low, moderate, and high ventilation rate condition in a balanced order. These conditions were established by covertly altering the fan speed of the exhaust ventilation system without changing other settings. Participants were not informed when or even whether the changes to bedroom ventilation would be executed. The bedroom environmental quality was monitored continuously and sleep quality was monitored using wrist-worn trackers. Tests of cognitive performance were conducted in the evening and morning. In twelve bedrooms where clear differences between the three ventilation conditions occurred, as indicated by the measured CO2 concentrations, participants had significantly less deep sleep, more light sleep and more awakenings at lower ventilation rate conditions. In twenty-three bedrooms where a clear difference in ventilation rate between the high and low ventilation conditions was observed, as confirmed by the measured CO2 concentrations, the deep sleep was significantly shorter in the low ventilation rate condition. No differences in cognitive performance between conditions were observed. At lower ventilation rate conditions, the concentrations of CO2 increased, as did the relative humidity, while bedroom temperatures remained unchanged. The present results, which were obtained in actual bedrooms, confirm the findings in previous studies of a positive effect of increased ventilation on sleep quality. Further studies with larger populations and better control of bedroom conditions, particularly ventilation, are required.

Time-resolved dynamic disability adjusted life-years estimation.

The quantification of how healthy the indoor air is, is a complex issue comprising of a large number of contaminants of various sources. The health implication of exposure to each of the contaminant deemed of importance can be expressed using Disability Adjusted Life Years (DALYs). The sum of all DALYs indicates how harmful the indoor air was during the investigated time-frame. This metric was originally developed by the World Bank and the WHO. In 2012, Logue et. al described two methods to estimate the DALYs related to exposure to contaminants in the indoor air based on the yearly mean exposure concentration of a population. The downside of these methods is that, when detailed exposure concentration profiles are available the method results in a loss of information. A novel method was developed to estimate DALYs originating from exposure to indoor pollutants that can be used for time-resolved exposure concentration data without this loss of information: Dynamic DALYs. The advantage of this method is that it can be calculated in real-time and for short or long periods of data. As such it can be used for pin-pointing problematic events in the exposure profile of a person and, as it can be calculated in real-time, makes it a candidate for use in automated optimization problems. The use of Dynamic DALYs is demonstrated for a simulation case-study of an occupied apartment. One continuously ventilated system (Dcont) and one smart ventilation system (Dsmart) are compared. Sources of typically indoor generated Volatile Organic Compounds (VOCs) were added and the related exposure profile and Dynamic DALY results of the working adult were analyzed. The results showcase detailed and more summative results with regards to health and energy use using the novel indicator. For Dcont and Dsmart the total Dynamic DALYs are 2.2 years and 8.6 years, respectively (population of 100 000, duration of 1 year), for the VOCs and sources considered in the analysis.

A survey of bedroom ventilation types and the subjective sleep quality associated with them in Danish housing.

We performed a survey of the types of bedroom ventilation in Danish dwellings (January-February 2020) and the associated subjective sleep quality. Five hundred and seventeen people responded. Their median age was 33 years old and 55.4% of them were males. We used an online questionnaire and collected information on the type of bedroom ventilation, bedroom airing behaviour by the respondents, the bedroom environment, building surroundings and location, and sleep disturbance caused by stuffy air, noise, and the thermal environment. Subjective sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI); its median among respondents was >5 indicating reduced sleep quality. 35.4% of the bedrooms had mechanical, 24.6% exhaust, and 40.0% natural ventilation. Sleeping in a bedroom with mechanical ventilation tended to reduce sleep disturbance. The absence of mechanical ventilation and the presence of carpet in the bedroom were all associated with stuffy air causing sleep disturbance, which was the second most sleep disturbing factor. PSQI increased significantly with increased sleep disturbance. People who reported that their sleep was disturbed by stuffy air or "too warm" conditions opened windows frequently during the day or night, but no association was found between PSQI and bedroom airing behaviours. Our results are valid for the heating season and the survey would have to be repeated in the non-heating season to permit generalization of the findings. The results present associations and are qualitative, so field measurements are necessary to validate the present observations and provide further explanations.

Overview and comparison of Legionella regulations worldwide.

BACKGROUND: Legionnaires disease occurs worldwide. Many authorities have guidelines and regulations to prevent and control Legionella in water systems. These regulations are based on often very limited field and laboratory observations and measurements. They are, therefore, very different from country to country. This article aims to map the existing regulatory framework of worldwide Legionella control to assess the feasibility of regulatory unification. METHODS: This article gives an overview of the different standards, guidelines, and recommendations as well as how various authorities and/or countries deal with Legionella infection. A 3-step process is followed to identify current regulations. RESULTS: Although Legionella is a global concern with a common scientific base, the regulatory framework is different from country to country. The current guidelines and standards are not the best possible. Despite different regulatory frameworks, there is still broad unification of underlying principles. Common principles across regulations are avoiding and monitoring critical spots, avoiding water stagnation, and maintaining sufficiently high temperature (above 60°C, below 25°C). Differences between regulations are target group and dangerous Legionella concentration levels. CONCLUSIONS: The comparative analysis of the framework is a good starting point for reaching future regulatory unification based on common ground.